Biology 2601A/B Lecture Notes - Lecture 5: Cytochrome C, Nadh Dehydrogenase, Lipid Bilayer

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Lecture 05: Energy - Respiration & Mitochondria
Last Lecture: The process of photosynthesis, how it generates ATP from sunlight and water, and how it
uses that ATP and NADPH to fix atmospheric carbon into forms that plants can metabolize or store.
This Lecture: How organisms (plants and animals) use the stored carbons to generate the form of energy
that cells can use (i.e. respiration). Cells can only use ATP as the currency of energy. Even though thee’s
a lot of potential energy stored in reduced carbon molecules like starch and sugar, cells a’t use the
directly. Plants must first convert these compounds to ATP.
Plants Autotrophic (produce their own food via photosynthesis and use it as energy)
Animals Heterotrophic
do’t podue thei o eeg,
get it from outside world)
Plant Respiration
- Occurs mostly in the mitochondria
- Photorespiration is also respiration
- How Do Plants Respire? They take the starch/sugars synthesized from photosynthesis and convert it
into simple sugars that are put through Glycolysis, where a little bit of ATP is produced. The big payoff of
Glycolysis is pyruvic acid (an organic acid) which then goes to the mitochondria through the Citric Acid
Cle. This does’t podue a lot of ATP, ut it does podue eduig euialets NADH2 and FAD,
which go to the ETC. Most of the ATP is produced via oxidative phosphorylation which occurs in the
inner membrane of the mitochondria.
The majority of plant respiration is primarily fueled by carbohydrates produced by plants
Note: not all of the carbon that fixed goes into the starch and simple sugars, some of it is shuttled off to make
things like cellulose which is used in the cell walls, or secondary metabolites that help protect the plant from the
environment
Animal Respiration
- Animals rely on different forms of carbon (carbs, fats, and proteins) to power respiration.
- They can really on sugars (a humming bird eats a lot of simple sugars), but most animals store sugars
as glycogen (which they can break down in glycolysis).
- They can also break down some amino acids which will feed into the CAC.
- “oe aials stoe a lot of fat i thei adipose tissue, hih does’t go though glolsis, ut though
β-oxidation which produces substrates that go right to the CAC.
Animals approach this from more than one direction, but in plants it is more straightforward
Herbivores/Omnivores - direct
consumption of plant carbohydrates
Carnivores - consumption of
glycogen and protein from prey
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Plant and Animal Respiration have Glycolysis in Common:
- start off with simple sugar (plants manufacture sucrose through photosynthesis, but sucrose is a
disaccharide so it must be broken down into its components glucose and fructose)
- glucose enters glycolysis and in the early parts of glycolysis, 2 ATP must be invested to phosphorylate
glucose into glucose 6-phosphate and to phosphorylate fructose 6-phosphate into fructose 1,6-
bisphosphate which is broken down into two 3 carbon molecules (2 G3P molecules). The G3P molecules
proceed through glycolysis and each yield 2 ATP so the net payoff of 1 glucose entering glycolysis is 2
ATP, 2 NADH (reducing equivalent), and 2 pyruvates (the big payoff).
Note: Where the animals differ is that they can also take this stored form of carbohydrate called
glycogen and break it down using enzymes. This process yields glucose 1-phosphate which can be
transformed into glucose 6-phosphate ad go oto glolsis. You do’t hae to iest ATP to
phosphorylate initial glucose because glycogen phosphorylase does it for you. So, the metabolism of
glycogen, compared to glucose, yields more ATP from glycolysis.
Fate of Pyruvate
If there is enough oxygen (aerobic):
- pyruvate is shuttled to mitochondria for CAC and then Oxidative Phosphorylation
If thee is’t eough oge aaeoi:
- fermentation
Types of Fermentation
1) Lactic Acid Fermentation
- Pyruvate is converted to Lactate (Lactic Acid) by the enzyme lactate dehydrogenase
- Lactate can buildup in the muscle or be exported into blood
- This is a way to regenerate the substrates (2 NAD+) needed for glycolysis to run temporarily
2) Ethanol Fermentation
- When yeast get a lot of glucose (from malted barley), but not much O2, then they take glucose through
glycolysis and produce pyruvate but instead of making lactate, they make ethanol.
- Whe ees of the ap fail iludig goldfish do’t get eough O2, their muscles go through
glycolysis, and pyruvate is formed but instead of forming lactate from pyruvate like other animals, they
form ethanol from pyruvate which they excrete through their gills
3) Opine Fermentation
- Aaeoi feetatio  olluss: The podue puate fo glolsis, ut do’t tu it ito
lactate, like other animals, or ethanol. Istead, the odese it ith a aio aid to ake opies if
pyruvate is condensed w/alaie it’s alled alanopie, if it’s odesed /lsie it’s alled lsopie, et.
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Document Summary

Last lecture: the process of photosynthesis, how it generates atp from sunlight and water, and how it uses that atp and nadph to fix atmospheric carbon into forms that plants can metabolize or store. This lecture: how organisms (plants and animals) use the stored carbons to generate the form of energy that cells can use (i. e. respiration). Cells can only use atp as the currency of energy. Even though the(cid:396)e"s a lot of potential energy stored in reduced carbon molecules like starch and sugar, cells (cid:272)a(cid:374)"t use the(cid:373) directly. Plants must first convert these compounds to atp. Plants autotrophic (produce their own food via photosynthesis and use it as energy) Animals heterotrophic (cid:894)do(cid:374)"t p(cid:396)odu(cid:272)e thei(cid:396) o(cid:449)(cid:374) e(cid:374)e(cid:396)g(cid:455), get it from outside world) Carnivores - consumption of glycogen and protein from prey. They take the starch/sugars synthesized from photosynthesis and convert it into simple sugars that are put through glycolysis, where a little bit of atp is produced.

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